Because a terminal can move in a mobile communication network, a network needs to always detect the location of the terminal, and needs to seamlessly and efficiently deliver data transmitted through another network to the terminal.
To this end, the mobile communication network supports handover and roaming. Handover smoothly maintains a telephone call of the terminal moving between a cell of a base station and that of another base station, and roaming smoothly maintains a telephone call of the terminal moving between an optional provider network and another provider network. In this regard, mobility management refers to the continuous management of a location, at which the terminal is positioned in the mobile communication network, in order to provide the terminal with a seamless mobile communication service as described above.
A serious problem is that an IP address is a very limited resource. Specifically, in a situation where it is difficult to currently assign even one IP address to the Mobile Node (MN), it is actually impossible to assign an IP address to the MN without restriction.